JP7462383B2 - Cleaning method and plasma processing apparatus - Google Patents

Description

This disclosure relates to a cleaning method and a plasma processing apparatus.

It has been proposed to supply a large amount of gas into a processing vessel, generate shock waves due to the rise in pressure, and use the shock waves to detach particles adhering to the inside of the processing vessel, which are then exhausted by the viscous force of the gas (see, for example, Patent Document 1).

JP 2005-243915 A

However, the above method may not be able to completely remove particles from within the processing vessel. For example, particles may remain on the edge ring that is placed around the semiconductor wafer (hereafter referred to as "wafer") on the mounting table and its surroundings. When this happens, the particles are attracted to the outermost periphery of the wafer placed on the mounting table, affecting the processing of the wafer and lowering the yield and productivity. Furthermore, even if particles are generated from parts placed in the processing vessel other than around the mounting table, they may affect the processing of the wafer.

This disclosure provides technology that can efficiently remove particles.

According to one aspect of the present disclosure, there is provided a cleaning method comprising the steps of: (a) supplying a cleaning gas into a processing vessel; (b) supplying high frequency power for generating plasma to either a first electrode on which a substrate is placed in the processing vessel or a second electrode opposed to the first electrode; (c) applying a negative voltage to an edge ring provided around the substrate; and (d) generating plasma from the cleaning gas and performing a cleaning process using the plasma.

According to one aspect, particles can be removed efficiently.

1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to an embodiment; 1 is a flowchart showing an example of a cleaning method according to an embodiment. 4 is a time chart showing an example of a cleaning method according to an embodiment. FIG. 4 is a diagram for explaining a cleaning action according to an embodiment. FIG. 13 is a diagram showing the results of a pseudo experiment on the cleaning effect according to the embodiment.

Below, a description will be given of a mode for carrying out the present disclosure with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicate descriptions may be omitted.

[Plasma Processing Apparatus]
A plasma processing apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the plasma processing apparatus 1 according to an embodiment.

The plasma processing apparatus 1 according to this embodiment is a capacitively coupled parallel plate plasma processing apparatus, and has a cylindrical processing vessel 10 made of, for example, aluminum whose surface has been anodized. The processing vessel 10 is grounded.

A support table 14 is placed on the bottom of the processing vessel 10 via an insulating plate 12 made of ceramics or the like, and a mounting table 16 is provided on the support table 14. The support table 14 and the mounting table 16 are made of, for example, aluminum.

An electrostatic chuck 20 is provided on the upper surface of the mounting table 16, which attracts and holds a wafer W, which is an example of a substrate, by electrostatic force. The electrostatic chuck 20 has a structure in which an electrode 20a made of a conductive film is sandwiched between a pair of insulating layers 20b or insulating sheets. The wafer W is placed on the electrostatic chuck 20. A power source 22 is connected to the electrode 20a. The wafer W is attracted and held on the electrostatic chuck 20 by electrostatic force such as Coulomb force generated by a DC voltage supplied from the power source 22.

A conductive edge ring 24 made of, for example, silicon is arranged around the wafer W to improve the uniformity of the plasma processing. A cylindrical cover ring 26 made of, for example, quartz is arranged around the edge ring 24 and extends to the sides of the mounting table 16 and the support table 14.

A coolant chamber 28 is provided inside the support table 14, for example in a ring shape. A heat exchange medium, for example cooling water, at a predetermined temperature is supplied from an external chiller unit via pipes 30a and 30b to the coolant chamber 28, and circulates. This allows the temperature of the wafer W on the mounting table 16 to be controlled by the temperature of the heat exchange medium. In addition, a heat transfer gas, for example He gas, from a heat transfer gas supply mechanism is supplied between the upper surface of the electrostatic chuck 20 and the rear surface of the wafer W via a gas supply line 32, which improves heat transfer between the mounting table 16 and the wafer W and enhances the temperature controllability of the wafer W.

The plasma processing apparatus 1 includes a first high-frequency power supply 48 and a second high-frequency power supply 90. The first high-frequency power supply 48 is a power supply that generates a first high-frequency power (hereinafter also referred to as "HF power"). The first high-frequency power has a frequency suitable for generating plasma. The frequency of the first high-frequency power is, for example, within a range of 27 MHz to 100 MHz. The first high-frequency power supply 48 is connected to the mounting table 16 (lower electrode) via a matching device 46 and a power feed rod 47. The matching device 46 has a circuit for matching the output impedance of the first high-frequency power supply 48 with the impedance of the load side (lower electrode side). The first high-frequency power supply 48 may be connected to the shower head (upper electrode) 34 via the matching device 46. The first high-frequency power supply 48 constitutes an example of a plasma generating unit.

The second high frequency power supply 90 is a power supply that generates a second high frequency power (hereinafter also referred to as "LF power"). The second high frequency power has a frequency lower than that of the first high frequency power. When the second high frequency power is used together with the first high frequency power, the second high frequency power is used as a high frequency power for a bias voltage for attracting ions to the substrate W. The frequency of the second high frequency power is, for example, within a range of 400 kHz to 13.56 MHz. The second high frequency power supply 90 is connected to the mounting table 16 (lower electrode) via a matching device 88 and a power feed rod 89. The matching device 88 has a circuit for matching the output impedance of the second high frequency power supply 90 with the impedance of the load side (lower electrode side).

It is to be noted that the plasma may be generated using the second high frequency power, i.e., using only a single high frequency power, without using the first high frequency power. In this case, the frequency of the second high frequency power may be a frequency greater than 13.56 MHz, for example, 40 MHz. The plasma processing apparatus 1 may not include the first high frequency power supply 48 and the matching box 46. The second high frequency power supply 90 constitutes an example of a plasma generating section. It is to be noted that the mounting table 16 may not include the electrostatic chuck 20.

A shower head 34 is provided above the mounting table 16 at a position facing the mounting table 16. Between the shower head 34 and the mounting table 16 is a plasma generation space 10S in which plasma is generated. The shower head 34 functions as an upper electrode with respect to the mounting table 16 which functions as a lower electrode.

The shower head 34 is supported on the upper part of the processing vessel 10 via an insulating shielding member 42. The shower head 34 has an electrode plate 36 having a large number of gas holes 37, and an electrode support 38 that detachably supports the electrode plate 36 and is made of a conductive material, for example, aluminum whose surface has been anodized. The electrode plate 36 is made of silicon or SiC. A gas diffusion chamber 40 is provided inside the electrode support 38, and a large number of gas pipes 41 extend downward from the gas diffusion chamber 40, with the tips of the gas pipes 41 being gas holes 37.

The electrode support 38 is fitted with a gas inlet 62 for introducing gas into the gas diffusion chamber 40, and a gas supply pipe 64 is connected to the gas inlet 62. A gas supply unit 66, a mass flow controller (MFC) 68, and an opening/closing valve 70 are connected to the gas supply pipe 64, in that order from the upstream side. Gas is supplied from the gas supply unit 66, and the flow rate and supply timing are controlled by the mass flow controller 68 and the opening/closing valve 70. The gas passes from the gas supply pipe 64 through the gas inlet 62 to the gas diffusion chamber 40, and is introduced into the plasma generation space 10S in a shower-like manner from the gas hole 37 via the gas pipe 41.

The plasma processing apparatus 1 includes a power supply 50 and a power supply 94. The power supply 50 is connected to the shower head 34. The power supply 50 applies a voltage to the shower head 34 to draw positive ions in the plasma generated in the plasma generation space 10S to the electrode plate 36. The power supply 94 is connected to the mounting table 16. The power supply 94 applies a voltage to the mounting table 16 to draw positive ions in the plasma generated in the plasma generation space 10S to the mounting table 16. The power supplies 50 and 94 may be bipolar power supplies.

An exhaust port 78 is formed at the bottom of the processing vessel 10 and is connected to an exhaust unit 80 via an exhaust pipe 81. An exhaust path connected to the exhaust port 78 is provided with an exhaust plate 77 that captures or reflects the plasma generated in the plasma generation space 10S to prevent leakage to the exhaust unit 80. The exhaust plate 77 may be made of an aluminum material coated with ceramics such as yttria (Y ₂ O ₃ ).

The exhaust section 80 has an Adaptive Pressure Control (APC) valve 82, a Turbo Molecular Pump (TMP) 83, and a dry pump 84.

A turbo molecular pump 83 and a dry pump 84 are connected to the exhaust pipe 81 via an automatic pressure control valve 82. After the dry pump 84 roughly evacuates the inside of the processing vessel 10, the turbo molecular pump 83 evacuates the inside of the processing vessel 10. At that time, the pressure is controlled by adjusting the opening of the automatic pressure control valve 82.

A loading/unloading port 85 for the wafer W is provided on the side wall of the processing vessel 10, and the loading/unloading port 85 can be opened and closed by a gate valve 86. In a processing apparatus configured as described above, when performing a plasma process such as etching, the gate valve 86 is first opened. Then, the wafer W held by the transfer arm is loaded into the processing vessel 10 via the loading/unloading port 85, the wafer W is received from the transfer arm using a lifter pin, and the wafer W is placed on the mounting table 16.

Processing gas is supplied from the gas supply unit 66 and is supplied in a shower-like manner from the gas hole 37 through the gas pipe 41 into the processing vessel 10. In addition, the inside of the processing vessel 10 is evacuated by the exhaust unit 80.

The plasma processing apparatus 1 is provided with a control unit 200 that controls the operation of the entire apparatus. The control unit 200 may be a computer equipped with a processor, a storage unit such as a memory, an input device, a display device, a signal input/output interface, etc. The control unit 200 controls each part of the plasma processing apparatus 1. In the control unit 200, an operator can use the input device to input commands to manage the plasma processing apparatus 1. In addition, the control unit 200 can visualize and display the operating status of the plasma processing apparatus 1 using the display device. Furthermore, the storage unit stores a process control program, a cleaning control program, and recipe data.

The processor executes a process control program to perform a predetermined plasma processing on the wafer W. The control unit 200 also executes a cleaning control program to clean the edge ring 24 and its surroundings, namely the outer periphery of the wafer W and the cover ring 26.

[Cleaning process]
Next, an example of a cleaning process performed by the plasma processing apparatus 1 according to this embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a flow chart showing an example of the cleaning process according to this embodiment. Fig. 3 is a time chart showing an example of the cleaning process according to this embodiment. The cleaning process method according to this embodiment is controlled by the control unit 200.

The cleaning process is performed during the processing of the wafers W by the plasma processing apparatus 1. The timing of the cleaning process is not limited to any one of the above, but may be, for example, a cleaning process performed after each wafer W is processed, or a cleaning process may be performed once after a predetermined number of wafers W are processed. The cleaning process may be performed periodically or irregularly. It may also be performed immediately before the start of a lot containing 25 wafers W, immediately after the end of the lot, or during an idle period between lots. The wafers W are removed before this process is started, and the following cleaning process is started with no wafers W placed on the electrostatic chuck 20.

When this process is started, the control unit 200 evacuates the inside of the processing vessel 10 to a predetermined pressure by the exhaust unit 80 (step S10). Next, the control unit 200 supplies _O2 gas from the gas supply unit 66 and adjusts the pressure inside the processing vessel 10 (step S12). _O2 gas is an example of a cleaning gas, and the cleaning gas is not limited to _O2 gas and may be ozone gas as long as it contains O.

Next, the control unit 200 applies the HF power output from the first high frequency power supply 48 to the mounting table 16 (step S14). Next, the control unit 200 applies a DC voltage of -500 V or more and less than 0 V output from the power supply 94 to the mounting table 16 (step S16).

Next, the control unit 200 determines whether a predetermined time has elapsed (step S18), executes the process of step S16 until the predetermined time has elapsed, and proceeds to step S20 once the predetermined time has elapsed.

Next, in step S20, the control unit 200 stops the application of the DC voltage from the power source 94. Next, the control unit 200 stops the application of the HF power (step S22), stops the exhaust and pressure adjustment by the exhaust unit 80, stops the supply of _O2 gas (step S24), and ends this process.

According to the cleaning process according to the present embodiment described above, as shown in FIG. 3A, the supply of _O2 gas (Gas ON), the application of HF power (RF ON), and the application of DC voltage (DC ON) are performed almost simultaneously. However, the application of HF power may be performed before the application of DC voltage. The supply of _O2 gas is stopped (Gas OFF), the application of HF power is stopped (RF OFF), and the application of DC voltage is stopped (DC OFF) almost simultaneously. However, the application of HF power may be stopped after the application of DC voltage is stopped.

In the cleaning process according to this embodiment, _O2 gas is converted into plasma by HF power, and in a state in which _O2 plasma is generated in the plasma generating space 10S, a negative DC voltage is applied to the edge ring 24. As a result, as shown in FIG. 4, positive ions in the plasma are attracted to the edge ring 24 to which the negative DC voltage is applied, the outer periphery of the wafer W, and the cover ring 26.

As a result, reaction products adhering to the edge ring 24, the outer periphery of the wafer W, and the cover ring 26 are peeled off by physical collision of the ions. The peeled off reaction products are exhausted from the exhaust section 80 and removed to the outside of the processing vessel 10.

As a result, by applying a negative DC voltage to the edge ring 24 while plasma is generated, particles adhering to the outer periphery of the wafer W, the edge ring 24, and the cover ring 26, which are the objects to be cleaned, shown in area Ar in Figure 4, can be effectively removed.

As shown in FIG. 3(b), after _O2 gas is supplied and HF power is applied, a cleaning process may be performed by _O2 plasma without applying a DC voltage (DC OFF), and a DC voltage may be applied in the middle to continue the cleaning process. According to this, while the DC voltage is not applied, chemical cleaning is mainly performed by radicals in the _O2 plasma, and after the DC voltage is applied, physical cleaning is performed by ions in the _O2 plasma. This also makes it possible to efficiently remove particles attached to the cleaning target, and to improve the cleaning effect. Furthermore, the timing of turning on and off the DC voltage shown in FIG. 3(b) may be reversed. This also makes it possible to mainly perform physical cleaning by ions in the _O2 plasma while the DC voltage is applied, and mainly perform chemical cleaning by radicals in the _O2 plasma while the DC voltage is not applied. This also makes it possible to improve the cleaning effect.

In the cleaning process in this embodiment, waferless dry cleaning (WLDC) was performed without placing a wafer W on the mounting table 16. In this case, since no wafer W is placed on the mounting table 16, the surface of the electrostatic chuck 20 is exposed to plasma. Therefore, in order to prevent the electrostatic chuck 20 from being damaged by the plasma, it is preferable that the negative voltage applied from the power supply 94 is a voltage of -500 V or more and less than 0 V.

However, the cleaning process in this embodiment may be performed with a dummy wafer or the like placed on the mounting table 16. In this case, the surface of the electrostatic chuck 20 is not exposed to plasma, so the electrostatic chuck 20 is less likely to be damaged during the cleaning process. For this reason, in this case, a negative voltage of -500 V or less may be applied from the power supply 94.

[effect]
Finally, an example of the effect of the cleaning process according to this embodiment will be described with reference to FIG. 5. FIG. 5 is a diagram showing the results of an experiment for simulating the cleaning effect according to one embodiment. In this experiment, as shown in FIG. 5(a), etching was performed in a state in which an organic film T was formed on the edge ring 24. Then, the etching rate of the organic film T was measured to simulate the effect of cleaning the reaction product on the edge ring 24. The process conditions at this time were as follows.

<Process conditions>
Gas type: _O2 gas HF power ON
LF power OFF
Fig. 5B shows the etching rate when the organic film T was etched under the above process conditions. The etching rate when a DC voltage was applied to the edge ring 24 (DC = -100 V) shown on the right side of Fig. 5B was 20% or more higher than the etching rate when no DC voltage was applied to the edge ring 24 (DC = 0 V) shown on the left side of Fig. 5B.

From the above, it can be seen that by applying a negative DC voltage to the edge ring 24 while plasma is generated, ions can be attracted to the edge ring 24, effectively enhancing the cleaning effect of the edge ring 24 and its surroundings.

In addition, in the cleaning method according to this embodiment, HF power is applied to convert the gas into plasma, and then a negative DC voltage is applied to the edge ring 24 to attract ions, thereby cleaning the edge ring 24 and its surroundings.

However, this is not limited to the above, and LF power or RF power with a frequency similar to that of the LF power may be applied to the edge ring 24 after applying HF power to turn the gas into plasma, thereby cleaning the edge ring 24 and its surroundings. Furthermore, LF power or RF power with a frequency similar to that of the LF power may be applied to the edge ring 24 after applying HF power to turn the gas into plasma, and a DC voltage may be applied to the edge ring 24 to clean the edge ring 24 and its surroundings.

Also, negatively charged particles can be cleaned by applying a positive DC voltage.

In addition, in the cleaning processing method according to this embodiment, HF power is used as the high frequency power for generating plasma, but LF power or microwave power may also be used.

The cleaning method and plasma processing apparatus according to the disclosed embodiment should be considered in all respects as illustrative and not restrictive. The above-described embodiment can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above-described embodiments can be configured in other ways without any contradiction, and can be combined without any contradiction.

The plasma processing apparatus disclosed herein can be applied to any type of apparatus, including ALD (Atomic Layer Deposition) apparatus, Capacitively Coupled Plasma (CCP), Inductively Coupled Plasma (ICP), Radial Line Slot Antenna, Electron Cyclotron Resonance Plasma (ECR), and Helicon Wave Plasma (HWP).

1 ... plasma processing apparatus 10 ... processing vessel 16 ... mounting table (lower electrode)
20...electrostatic chuck 24...edge ring 26...cover ring 34...shower head (upper electrode)
48... First high frequency power source 50... Power source 66... Gas supply unit 80... Exhaust unit 82... APC valve 83... TMP
84... dry pump 90... second high frequency power source 94... power source 200... control unit

Claims (15)

(a) plasma processing a substrate in a processing chamber;
(b) after (a), supplying a cleaning gas into the processing vessel;
(c) supplying high frequency power for generating plasma to either a first electrode on which a substrate is placed in the processing chamber or a second electrode opposed to the first electrode;
(d) applying a negative voltage to an edge ring disposed around the substrate;
(e) performing a cleaning process in which, with the substrate or a dummy wafer placed on the first electrode, plasma is generated from the cleaning gas , and reaction products adhering to the outer periphery of the substrate and the edge ring are removed by the plasma;
The cleaning method according to claim 1, A processing vessel;
a mounting table that functions as a first electrode in the processing chamber and supports a substrate thereon;
an edge ring disposed on the mounting table so as to surround the substrate;
A second electrode that is disposed opposite the mounting table and constitutes a plasma generating unit;
A method for cleaning a plasma processing apparatus, comprising:
(a) supplying a cleaning gas into the processing vessel;
(b) supplying high frequency power for generating plasma to the second electrode;
(c) applying a negative voltage to the edge ring;
(d) generating plasma from the cleaning gas and performing a cleaning process to remove reaction products adhering to the outer periphery of the substrate and the edge ring by using the plasma;
The cleaning method according to claim 1, The step of performing the cleaning process includes placing a substrate on the placement table .
The cleaning method according to claim 2 . the step of applying a negative voltage to the edge ring includes applying a negative DC voltage;
The cleaning method according to any one of claims 1 to 3. the step of applying a negative voltage to the edge ring includes applying a voltage of −500 V or more and less than 0 V;
The cleaning method according to claim 4. The step of applying a negative voltage to the edge ring applies a voltage of −500 V or less.
The cleaning method according to claim 4. The step of applying a negative voltage to the edge ring further includes supplying a high-frequency power having a frequency lower than that of the high-frequency power for generating the plasma to the edge ring.
The cleaning method according to any one of claims 1 to 6. The cleaning gas is an oxygen-containing gas.
The cleaning method according to any one of claims 1 to 7. (f) determining whether a predetermined time has elapsed after the start of the cleaning process ;
(g) stopping the supply of the cleaning gas, the supply of the high frequency power for plasma generation, and the application of the negative voltage when it is determined in the determining step that a predetermined time has elapsed.
The cleaning method according to any one of claims 1 to 8. In the step ( g ), the supply of the cleaning gas, the supply of the high frequency power for plasma generation, and the application of the negative voltage are stopped simultaneously.
The cleaning method according to claim 9. In the step ( g ), after the application of the negative voltage is stopped, the supply of high frequency power for generating the plasma is stopped.
The cleaning method according to claim 9. the step of supplying high frequency power for generating plasma , the step of applying a negative voltage to the edge ring, and the step of performing the cleaning process are performed simultaneously;
The cleaning method according to any one of claims 1 to 11. a step of applying a negative voltage to the edge ring is performed after the step of supplying high frequency power for generating plasma .
The cleaning method according to any one of claims 1 to 11. A processing vessel;
a first electrode on which a substrate is placed within the processing chamber;
a second electrode facing the first electrode;
an edge ring disposed around the periphery of the substrate;
A plasma processing apparatus having a control unit,
The control unit is
(a)) subjecting a substrate to plasma processing in a processing chamber;
(b) after (a), supplying a cleaning gas into the processing vessel;
(c) supplying a first high frequency power for generating plasma to either the first electrode or the second electrode;
(d) supplying a negative voltage and/or a second radio frequency power having a frequency lower than the first radio frequency power to the edge ring;
(e) performing a cleaning process in which, with the substrate or tammy wafer placed on the first electrode, plasma is generated from the cleaning gas, and reaction products adhering to the outer periphery of the substrate and the edge ring are removed by the plasma;
The plasma processing apparatus controls the A processing vessel;
a mounting table that functions as a first electrode in the processing chamber and supports a substrate thereon;
an edge ring disposed on the mounting table so as to surround the substrate ;
A second electrode that is disposed opposite the mounting table and constitutes a plasma generating unit ;
A plasma processing apparatus having a control unit,
The control unit is
(a) supplying a cleaning gas into the processing vessel;
(b) supplying a first high frequency power for generating plasma to the second electrode;
(c) supplying a negative voltage and/or a second high frequency power having a frequency lower than the first high frequency power to the edge ring;
(d) generating plasma from the cleaning gas and performing a cleaning process to remove reaction products adhering to the outer periphery of the substrate and the edge ring by using the plasma;
The plasma processing apparatus controls the

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